Smoothen out edge after deletion
One quick and dirty method would be to use the circle select tool to quickly remove the strays—but that will not create sharp edges or a completely smooth mesh.

Have you tried the Subsurface Modifier? That could help. It is an absolute fundamental to smoothing a mesh and a MUST-learn.

But from a more professional standpoint—the topology of this model is way too complicated. The scan has created an accurate but wildly complicated form that contains triangles (the worst when you are creating almost anything—especially here when they are tiny). 

The ultimate (and most correct) workflow from here, to my knowledge, would be to retopologize the face. There are YouTube tutorials on “Retopo” and it’s worth the time to learn. This mask you have is what all game characters look like when they’re first sculpted—very complicated and dense with miniature triangles—then they have to go back and create a final clean version using the Retopo technique.

John